In 2005 and 2006, Black was linked to a series of scandals involving, among other things, the party-switching Rep. Michael P. Decker, and the North Carolina lottery, established the previous year. The proceedings led to convictions for several involved figures, including Decker, media and public relations consultant Kevin L. Geddings and political aide Meredith Norris. Decker testified under oath that he instigated a bribery scheme of which Black was alleged to be a "co-conspirator". Black has consistently denied those allegations.

Although Black was not indicted while serving as speaker, the situation drew ire from the North Carolina Republican Party, which involved the scandal in their November election campaigns.[4]

Black was re-elected in November 2006, over Republican political novice Hal Jordan. Meanwhile, he led efforts to increase the Democratic majority in the State House.

In December 2006, Black announced that he would not seek another term as Speaker.[5] That was followed in January 2007 by his announcement that he would not run for re-election to the House in 2008.[6]

Black pleaded guilty to a federal charge of public corruption on February 15, 2007, a felony carrying a maximum sentence of 10 years in prison and a $250,000 fine.[7] He admitted to accepting funds from chiropractors while their professional group had legislation pending in the North Carolina General Assembly. As a result, he resigned from the General Assembly on February 14, 2007.[8]

Federal prosecutors have said the plea deal with Black involves his assistance in their continued investigation into political corruption in North Carolina government.

Black's agreement with federal prosecutors did not protect him from state prosecution.[9] Indeed, days after his federal plea, he entered into a separate Alford plea agreement with the district attorney of Wake County, whose jurisdiction includes the state capital, Raleigh.[10]

On July 11, 2007, Black was sentenced by Judge Terrence Boyle to five years, three months in prison, three years of probation, and a $50,000 fine.[11] Black was sentenced in state court as well in 2007 and 2009, but was allowed to serve his state sentences concurrently with his federal prison time.[12][13]

In 2010, Black was released from federal prison in Georgia and returned to Mecklenburg County to serve the remaining six months of his term either at a halfway house or under house arrest.[14]